Tip portion structure of high-frequency probe and method for fabrication probe tip portion composed by coaxial cable

A tip portion structure of a probe to be pressed against a signal electrode of a DUT (device-under-test) placed on a device stage, the signal electrode of the DUT being located on an upper surface thereof and the DUT having a ground electrode on a lower surface thereof, the device stage having a conductive portion for contacting the ground electrode of the DUT and extending from beneath the DUT, said tip portion structure comprising:

• a tip substrate having an upper and a lower surface, the lower surface having a signal line formed thereon;
• a conductive ground plate covering the upper surface of the tip substrate;
• a plate spring positioned to resist upward pressure on said tip substrate;
• and
• a conductive ground block positioned against the lower surface of said tip substrate, a forward surface of the ground block being displaced from a forward end of the tip substrate by an amount such that the conductive ground block may make contact with the conductive portion of the device stage when the signal line of the tip substrate is in electrical contact with the signal electrode of the DUT,
• the signal line and the conductive ground plate thereby maintaining a spacing during contact with the DUT, the tip portion structure thereby maintaining a characteristic impedance during contact with the DUT.